Two-Dimensional Brickblock Arrangement in Bis-Fused Tetrathiafulvalene Semiconductors

Molecular packing arrangement is
a very important factor in the
charge carrier mobility of organic semiconductors, but its rational
design has not been established as yet. Two-dimensional (2D) lamellar
packing is an advantageous arrangement for high charge mobility, but
few examples have been reported thus far. Herein we show crystal structures
and the electronic properties of newly designed bis-fused tetrathiafulvalene
(TTF) semiconductors with hetero substituent groups with distinct
electronic effects. Unprecedented 2D lamellar alignment is achieved
in a single crystal, where the bis-fused TTF rings interact three
dimensionally with face-to-face and side-by-side intermolecular S···S
contacts up to a total of 20 sites per π molecule and form graphitelike
“brickblock” structure. The charge mobility of a single
crystal is as high as 0.78 cm2 V–1 s–1. Systematic investigations of the semiconductors
reveal a key role of intramolecular S···O interaction
between a bis-fused TTF ring and a methoxycarbonyl group in controlling
efficient arrangement, leading to high mobility.